Fluid sprinkling – spraying – and diffusing – Fluid pressure responsive discharge modifier* or flow... – Fuel injector or burner
Patent
1994-03-30
1995-02-21
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Fluid pressure responsive discharge modifier* or flow...
Fuel injector or burner
F02M 4304, F02M 4508
Patent
active
053908562
DESCRIPTION:
BRIEF SUMMARY
SUMMARY OF THE INVENTION
The present invention relates to fuel injectors for use in diesel engines and is concerned with so-called twin fuel injectors which are adapted to inject two different grades of fuel sequentially through the same injection nozzle.
In large diesel engines, such as those used for ship propulsion, heavy oil is used as a fuel as this is available at relatively low cost. The combustion characteristics of heavy oils are such that a delay period occurs between the fuel's injection into the cylinder and the start of combustion. This is an undesirable characteristic since it means that a relatively large volume of fuel is present in the cylinder when combustion starts and the rate of pressure rise in the cylinder is thus very high. This in turn means that high noise levels are emitted and high levels of stress are generated in the components of the engine.
A known solution to this problem is to use the pilot injection of a small quantity of fuel before the main fuel charge is injected. It is known that the same fuel can be used for the pilot and main injections through a single injector. It is also known that the pilot injection is more effective if a higher grade fuel is used for the pilot injection. A known method of achieving this is to pump the pilot fuel into the injector using a secondary pumping system as described in EP-A-0282819.
EP-A-0282819 discloses a fuel injector comprising a body defining a Rain fuel supply passage and a pilot fuel supply passage which communicate with the injection nozzle directly and via a non-return valve respectively. The main fuel supply passage is supplied with the main fuel by a conventional fuel injection pump and the pilot fuel supply passage communicates with a pilot fuel pump via a solenoid valve which is controlled by a complex timing control system.
The construction disclosed in this prior specification is complex bulky and expensive due to the necessity of providing the solenoid valve and the associated control system. Furthermore a second high pressure injection pump is required for the pilot fuel in addition to the usual high pressure injection pump required for the main fuel.
It is the object of the present invention to provide a fuel injector which is capable of injecting two different fuels sequentially and which overcomes the problems referred to above and which, in particular, requires only one high pressure injection pump and no control valve or control system to control the injection of the pilot fuel.
According to the present invention a fuel injector for use in a diesel engine adapted to inject two different fuels sequentially of the type comprising a body including an injection nozzle defining one or more injection orifices, a main fuel supply passage and a pilot fuel supply passage, which includes a first non-return valve arranged to prevent fuel flowing in it away from the injection nozzle, the nozzle being controlled by a valve needle which affords a surface directed towards the injection orifice(s) and exposed to a fuel supply gallery is characterised in that the body contains a cylinder which slidably receives a piston, that the main fuel passage communicates with the cylinder adjacent one end thereof, that the pilot fuel passage communicates with the cylinder adjacent the other end thereof and with a first outlet passage which communicates with the fuel gallery and includes a second non-return valve arranged to prevent fuel flowing from the fuel gallery into the pilot fuel passage and that a second outlet passage is provided which communicates with the fuel gallery and with the cylinder at a point intermediate its ends, whereby the main fuel passage communicates with the fuel gallery via the cylinder and the second outlet passage when the piston is at the said other end of the cylinder but not when it is at the said one end of the cylinder.
In use, the main fuel supply passage will be connected to a substantially conventional high pressure fuel injection pump whose outlet pressure varies cyclically but the pilot fuel supply pa
REFERENCES:
patent: 3394891 (1968-07-01), Voit
patent: 3403861 (1968-10-01), Eidtmann et al.
patent: 4258883 (1981-03-01), Hofmann et al.
patent: 4467963 (1984-08-01), Sisson et al.
patent: 4938193 (1990-07-01), Raufeisse et al.
patent: 4957085 (1990-09-01), Suerdlin
Kashnikow Andres
Ricardo Consulting Engineers Limited
Weldon Kevin P.
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